Showing papers on "Ultraviolet light published in 2012"
TL;DR: Deep-ultraviolet irradiation induces efficient condensation and densification of oxide semiconducting films by photochemical activation at low temperature, which is applicable to numerous metal-oxide semiconductors, and the performance (in terms of transistor mobility and operational stability) of thin-film transistors fabricated by this route compares favourably with that ofthin- film transistors based on thermally annealed materials.
Abstract: A method for annealing metal-oxide semiconductor films with deep-ultraviolet light yields thin-film transistors with performance comparable to that of thermally annealed devices, and widens the range of substrates on which such devices can be fabricated. Solution-processable metal-oxide semiconductors are attractive materials for low-cost, flexible electronics, but the need to anneal the deposited materials at relatively high temperatures limits the range of substrates on which such devices can be fabricated. Now Yong-Hoon Kim and colleagues demonstrate that irradiating the solution-cast films with deep ultraviolet light can obviate the need for an annealing step. In this system, photochemical activation serves essentially the same purpose as annealing, and the resulting semiconducting materials have device performance levels comparable to those produced using the high-temperature techniques. Amorphous metal-oxide semiconductors have emerged as potential replacements for organic and silicon materials in thin-film electronics. The high carrier mobility in the amorphous state, and excellent large-area uniformity, have extended their applications to active-matrix electronics, including displays, sensor arrays and X-ray detectors1,2,3,4,5,6,7. Moreover, their solution processability and optical transparency have opened new horizons for low-cost printable and transparent electronics on plastic substrates8,9,10,11,12,13. But metal-oxide formation by the sol–gel route requires an annealing step at relatively high temperature2,14,15,16,17,18,19, which has prevented the incorporation of these materials with the polymer substrates used in high-performance flexible electronics. Here we report a general method for forming high-performance and operationally stable metal-oxide semiconductors at room temperature, by deep-ultraviolet photochemical activation of sol–gel films. Deep-ultraviolet irradiation induces efficient condensation and densification of oxide semiconducting films by photochemical activation at low temperature. This photochemical activation is applicable to numerous metal-oxide semiconductors, and the performance (in terms of transistor mobility and operational stability) of thin-film transistors fabricated by this route compares favourably with that of thin-film transistors based on thermally annealed materials. The field-effect mobilities of the photo-activated metal-oxide semiconductors are as high as 14 and 7 cm2 V−1 s−1 (with an Al2O3 gate insulator) on glass and polymer substrates, respectively; and seven-stage ring oscillators fabricated on polymer substrates operate with an oscillation frequency of more than 340 kHz, corresponding to a propagation delay of less than 210 nanoseconds per stage.
1,074 citations
TL;DR: This review presents as much detailed information as possible that is available on various neurodegenerative disorders and their connection with oxidative stress to present a variety of therapeutic strategies designed to address these pathological processes.
771 citations
TL;DR: A photoresponsive supramolecular actuator is designed by integrating host–guest interactions and photoswitching ability in a hydrogel by integratingHost–guerilla interactions and Photoswitching Ability in a Hydrogel.
Abstract: The development of stimulus-responsive polymeric materials is of great importance, especially for the development of remotely manipulated materials not in direct contact with an actuator. Here we design a photoresponsive supramolecular actuator by integrating host-guest interactions and photoswitching ability in a hydrogel. A photoresponsive supramolecular hydrogel with α-cyclodextrin as a host molecule and an azobenzene derivative as a photoresponsive guest molecule exhibits reversible macroscopic deformations in both size and shape when irradiated by ultraviolet light at 365 nm or visible light at 430 nm. The deformation of the supramolecular hydrogel depends on the incident direction. The selectivity of the incident direction allows plate-shaped hydrogels to bend in water. Irradiating with visible light immediately restores the deformed hydrogel. A light-driven supramolecular actuator with α-cyclodextrin and azobenzene stems from the formation and dissociation of an inclusion complex by ultraviolet or visible light irradiation.
681 citations
TL;DR: Genetic variation in various sub-Saharan populations did not localize the origin of modern humans to a single geographic region within Africa; instead, it indicated a history of admixture and stratification, and illustrated the importance of African genomic diversity in understanding human evolutionary history.
Abstract: The history of click-speaking Khoe-San, and African populations in general, remains poorly understood. We genotyped ~2.3 million single-nucleotide polymorphisms in 220 southern Africans and found that the Khoe-San diverged from other populations ≥100,000 years ago, but population structure within the Khoe-San dated back to about 35,000 years ago. Genetic variation in various sub-Saharan populations did not localize the origin of modern humans to a single geographic region within Africa; instead, it indicated a history of admixture and stratification. We found evidence of adaptation targeting muscle function and immune response; potential adaptive introgression of protection from ultraviolet light; and selection predating modern human diversification, involving skeletal and neurological development. These new findings illustrate the importance of African genomic diversity in understanding human evolutionary history.
457 citations
TL;DR: In this article, the sulfamethazine (SMT) degradation exhibited a pseudo-first-order reaction pattern, and the degradation rate was influenced by the S2O82- dose and solution pH.
455 citations
TL;DR: Recent progress in the field of photoelectrochemical water oxidation is reviewed with emphasis on water-oxidation photoanodes inspired by the design of functionalized thin film semiconductors of typical dye-sensitized solar cells.
363 citations
TL;DR: A theoretical model consistent with corneal oxygen consumption experimental results during UV-A irradiation under different conditions is developed and it is suggested that the main photochemical kinetics mechanism is the direct interaction between Rf triplets and reactive groups of cornea proteins, which leads to the cross-linking of the proteins mainly through radical reactions.
Abstract: Purpose To model the photochemical kinetics of corneal cross-linking with riboflavin (Rf) and confirm the model through measured oxygen concentration experiments under varying energy input conditions by UV-A irradiance and temperature modulation in ex vivo porcine cornea. Methods A theoretical model was developed to describe the corneal cross-linking photochemical kinetics of Rf. After instillation with drops of Rf solution in distilled water, de-epithelialized porcine corneas were exposed to 365-nm ultraviolet light (UV-A) under varying irradiance and temperature. Oxygen concentration in the cornea at a known depth was monitored during UV-A illumination with a dissolved oxygen fiberoptic microsensor. Data from the oxygen experiments were used to confirm the model. Results On the basis of the known chemical reactions and diffusion rates of Rf and oxygen into the cornea, the authors developed a theoretical model consistent with corneal oxygen consumption experimental results during UV-A irradiation under different conditions. Oxygen concentration in the cornea is modulated by UV-A irradiance and temperature and quickly decreased at the beginning of UV-A exposure. The time-dependence of both Type-I and Type-II photochemical mechanisms in corneal cross-linking with Rf are discussed. Conclusions Using a chemical kinetics modeling approach, the authors developed a simple model that is in agreement with their experimental results on oxygen consumption in the cornea during corneal cross-linking with Rf. It is suggested that the main photochemical kinetics mechanism is the direct interaction between Rf triplets and reactive groups of corneal proteins, which leads to the cross-linking of the proteins mainly through radical reactions.
322 citations
TL;DR: It is shown that melanoma induction by ultraviolet A requires the presence of melanin pigment and is associated with oxidative DNA damage within melanocytes, and an unexpected and significant role for melanin within the melanocyte in melanomagenesis is described.
Abstract: Exposure to ultraviolet light is responsible for a large proportion of melanomas but the molecular mechanisms are unknown. In this study, melanoma is found to be induced in mice by UVA and UVB light in a pigment-dependent and -independent manner, respectively, resulting in different types of DNA damage.
303 citations
TL;DR: It is shown that relatively low levels of ultraviolet light, consistent with those found in nature, can induce toxicity of TiO2 nanoparticles to marine phytoplankton, the most important primary producers on Earth.
Abstract: Nanoparticulate titanium dioxide (TiO2) is highly photoactive, and its function as a photocatalyst drives much of the application demand for TiO2. Because TiO2 generates reactive oxygen species (ROS) when exposed to ultraviolet radiation (UVR), nanoparticulate TiO2 has been used in antibacterial coatings and wastewater disinfection, and has been investigated as an anti-cancer agent. Oxidative stress mediated by photoactive TiO2 is the likely mechanism of its toxicity, and experiments demonstrating cytotoxicity of TiO2 have used exposure to strong artificial sources of ultraviolet radiation (UVR). In vivo tests of TiO2 toxicity with aquatic organisms have typically shown low toxicity, and results across studies have been variable. No work has demonstrated that photoactivity causes environmental toxicity of TiO2 under natural levels of UVR. Here we show that relatively low levels of ultraviolet light, consistent with those found in nature, can induce toxicity of TiO2 nanoparticles to marine phytoplankton, the most important primary producers on Earth. No effect of TiO2 on phytoplankton was found in treatments where UV light was blocked. Under low intensity UVR, ROS in seawater increased with increasing nano-TiO2 concentration. These increases may lead to increased overall oxidative stress in seawater contaminated by TiO2, and cause decreased resiliency of marine ecosystems. Phototoxicity must be considered when evaluating environmental impacts of nanomaterials, many of which are photoactive.
297 citations
TL;DR: These findings offer fresh insight into the molecular mechanisms of radiation resistance and present themselves as new opportunities to study and control oxidative stress in eukaryotes, including mammalian cells and their cancer cell counterparts.
248 citations
TL;DR: A new finding is the specific UV-B-mediated induction of glucosinolates (GS), especially of 4-methylsulfinylbutyl GS and 4-methoxy-indol-3-ylmethyl GS, while carotenoids and Chl levels remained unaffected.
Abstract: Only a few environmental factors have such a pronounced effect on plant growth and development as ultraviolet light (UV). Concerns have arisen due to increased UV-B radiation reaching the Earth’s surface as a result of stratospheric ozone depletion. Ecologically relevant low to moderate UV-B doses (0.3–1 kJ m–2 d–1) were applied to sprouts of the important vegetable crop Brassica oleracea var. italica (broccoli), and eco-physiological responses such as accumulation of non-volatile secondary metabolites were related to transcriptional responses with Agilent One-Color Gene Expression Microarray analysis using the 2×204 k format Brassica microarray. UV-B radiation effects have usually been linked to increases in phenolic compounds. As expected, the flavonoids kaempferol and quercetin accumulated in broccoli sprouts (the aerial part of the seedlings) 24 h after UV-B treatment. A new finding is the specific UV-B-mediated induction of glucosinolates (GS), especially of 4-methylsulfinylbutyl GS and 4-methoxy-indol-3-ylmethyl GS, while carotenoids and Chl levels remained unaffected. Accumulation of defensive GS metabolites was accompanied by increased expression of genes associated with salicylate and jasmonic acid signaling defense pathways and up-regulation of genes responsive to fungal and bacterial pathogens. Concomitantly, plant pre-exposure to moderate UV-B doses had negative effects on the performance of the caterpillar Pieris brassicae (L.) and on the population growth of the aphid Myzus persicae (Sulzer). Moreover, insect-specific induction of GS in broccoli sprouts was affected by UV-B pre-treatment.
TL;DR: In this article, the authors demonstrate that pristine graphene can detect gas molecules at extremely low concentrations with detection limits as low as 158 parts-per-quadrillion (ppq) for a range of gases at room temperature.
Abstract: Graphene is widely regarded as one of the most promising materials for sensor applications. Here, we demonstrate that a pristine graphene can detect gas molecules at extremely low concentrations with detection limits as low as 158 parts-per-quadrillion (ppq) for a range of gas molecules at room temperature. The unprecedented sensitivity was achieved by applying our recently developed concept of continuous in situ cleaning of the sensing material with ultraviolet light. The simplicity of the concept, together with graphene’s flexibility to be used on various platforms, is expected to intrigue more investigations to develop ever more sensitive sensors.
TL;DR: In this paper, the authors show that the desirable route to extend the photocatalytic activity of a semiconductor from the ultraviolet to the visible light region is to narrow the band gap rather than to create localized mid-gap states.
Abstract: Approximately 15 nm thick nitrogen-doped lanthanum titanate (La2Ti2O7) nanosheets with a single-crystalline perovskite structure have been prepared by hydrothermal processing and subsequent heat treatment in NH3 at 600 °C. Doping nitrogen into the La2Ti2O7 nanosheets results in the narrowing of the band gap, extending the light absorption into the visible light region (∼495 nm). The nitrogen-doped La2Ti2O7 nanosheets not only show significant visible light photocatalytic activity toward the decomposition of methyl orange but also exhibit enhanced the ultraviolet light photocatalytic activity. The enhancement of photocatalytic activity originates from the narrowing of the band gap of La2Ti2O7 nanosheets. The results obtained show that the desirable route to extend the photocatalytic activity of a semiconductor from the ultraviolet to the visible light region is to narrow the band gap rather than to create localized mid-gap states. Open image in new window
TL;DR: In this article, the effects of oil content on lipid droplet distributions in the film-forming dispersions and emulsified films were evaluated and compared, and the possible relationship between some selected physical properties and microstructure of the films was also discussed.
TL;DR: The galvanized steel was found to be the most suitable for rainwater harvesting applications, with their resulting physical and chemical water quality parameters meeting the Korean guidelines for drinking water quality.
TL;DR: Sugar alcohol derivatives with multi azobenzene arms are photochemically and isothermally liquefied from a powdered solid upon irradiated with ultraviolet light at room temperature, and then solidified on irradiation with visible light, where the transition between solid and liquid are reversible.
Abstract: Sugar alcohol derivatives with multi azobenzene arms are photochemically and isothermally liquefied from a powdered solid upon irradiation with ultraviolet light at room temperature, and then solidified on irradiation with visible light, where the transition between solid and liquid are reversible. These compounds possess similar chemical structures to comb-like liquid crystalline oligomers.
Patent•
16 Aug 2012TL;DR: In this paper, a light-emitting device with a substrate including a substrate second upper surface provided between a substrate bottom surface and a substrate first upper surface in a height direction is presented.
Abstract: A light-emitting device includes a substrate including a substrate second upper surface provided between a substrate bottom surface and a substrate first upper surface in a height direction. A light-emitting element to emit ultraviolet light is provided on the substrate first upper surface. A protective element includes a protective element upper surface provided between the substrate first upper surface and the substrate second upper surface in the height direction. A frame is bonded to the substrate first upper surface via adhesive members to surround the light-emitting element. The frame includes a frame lower surface opposite to the substrate first upper surface and the substrate second upper surface in the height direction to provide a gap between the substrate first upper surface and the frame lower surface. A space in which the light-emitting element is provided communicates with an outside of the light-emitting device via the gap.
TL;DR: Data suggest that these collagen and PEG hydrogels exhibit the mechanical, physical and biological properties suitable for use as an injectable tissue scaffold for the treatment of a variety of simple and complex tissue defects.
TL;DR: In this paper, single crystal AlN provides a native substrate for Al-rich AlGaN that is needed for the development of efficient deep ultraviolet light emitting and laser diodes An absorption band centered around 47 eV (∼265 nm) with an absorption coefficient above 1000 cm−1 is observed in these substrates based on density functional theory calculations, substitutional carbon on the nitrogen site introduces absorption at this energy.
Abstract: Single crystal AlN provides a native substrate for Al-rich AlGaN that is needed for the development of efficient deep ultraviolet light emitting and laser diodes An absorption band centered around 47 eV (∼265 nm) with an absorption coefficient above 1000 cm−1 is observed in these substrates Based on density functional theory calculations, substitutional carbon on the nitrogen site introduces absorption at this energy A series of single crystalline wafers were used to demonstrate that this absorption band linearly increased with carbon, strongly supporting the model that CN- is the predominant state for carbon in AlN
TL;DR: Through a combination of these two ultra-strong materials, ANFs and graphene nanosheets, the resultant ANFGS can act as novel nanofillers for polymer reinforcement and be used as an additive for reinforcing the mechanical properties of poly(methyl methacrylate) (PMMA).
Abstract: Aramid macroscale fibers, also called Kevlar fibers, exhibit extremely high mechanical performance. Previous studies have demonstrated that bulk aramid macroscale fibers can be effectively split into aramid nanofibers (ANFs) by dissolution in dimethylsulfoxide (DMSO) in the presence of potassium hydroxide (KOH). In this paper, we first introduced the ANFs into the structure of graphene nanosheets through non-covalent functionalization through π–π stacking interactions. Aramid nanofiber-functionalized graphene sheets (ANFGS) were successfully obtained by adding the graphene oxide (GO)/DMSO dispersion into the ANFs/DMSO solution followed by reduction with hydrazine hydrate. The ANFGS, with ANFs absorbed on the surface of the graphene nanosheets, can be easily exfoliated and dispersed in N-methyl-2-pyrrolidone (NMP). Through a combination of these two ultra-strong materials, ANFs and graphene nanosheets (GS), the resultant ANFGS can act as novel nanofillers for polymer reinforcement. We used the ANFGS as an additive for reinforcing the mechanical properties of poly(methyl methacrylate) (PMMA). With a loading of 0.7 wt% of the ANFGS, the tensile strength and Young's modulus of the ANFGS/PMMA composite film approached 63.2 MPa and 3.42 GPa, which are increases of ∼84.5% and ∼70.6%, respectively. The thermal stabilities of ANFGS/PMMA composite films were improved by the addition of ANFGS. Additionally, the transparencies of the ANFGS/PMMA composite films have a degree of UV-shielding due to the ultraviolet light absorption of the ANFs in the ANFGS.
TL;DR: It is confirmed non-invasively that Riboflavin and UV-cross-linking induce changes in the corneal biomechanical properties, and those differences appear to be the result of changes in constituent properties of the cornea, and not a consequence ofChanges in Corneal thickness, geometry or IOP.
Abstract: A new technique is presented for the non-invasive imaging of the dynamic response of the cornea to an air puff inducing a deformation. A spectral OCT instrument combined with an air tonometer in a non-collinear configuration was used to image the corneal deformation over full corneal cross-sections, as well as to obtain high speed measurements of the temporal evolution of the corneal apex. The entire deformation process can be dynamically visualized. A quantitative analysis allows direct extraction of several deformation parameters, such as amplitude, diameter and volume of the maximum deformation, as well as duration and speed of the increasing deformation period and the recovery period. The potential of the technique is demonstrated on porcine corneas in vitro under constant IOP for several conditions (untreated, after riboflavin instillation and under cross-linking with ultraviolet light), as well as on human corneas in vivo. The new technique has proved very sensitive to detect differences in the deformation parameters across conditions. We have confirmed non-invasively that Riboflavin and UV-cross-linking induce changes in the corneal biomechanical properties. Those differences appear to be the result of changes in constituent properties of the cornea, and not a consequence of changes in corneal thickness, geometry or IOP. These measurements are a first step for the estimation of the biomechanical properties of corneal tissue, at an individual level and in vivo, to improve diagnosis and prognosis of diseases and treatments involving changes in the biomechanical properties of the cornea.
TL;DR: In this paper, a new manganese(II) coordination polymer, [Mn2(L1)4/3(L2)2]n (1) (L1 = 4′-(4-pyridyl)-4,2′:6′,4″-terpyridine, H2L2 = (4-phenyl)-2,6-bis(4-carboxyphenyl) pyridine), has been prepared and structurally characterized.
Abstract: A new manganese(II) coordination polymer, [Mn2(L1)4/3(L2)2]n (1) (L1 = 4′-(4-pyridyl)-4,2′:6′,4″-terpyridine, H2L2 = (4-phenyl)-2,6-bis(4-carboxyphenyl)pyridine), has been prepared and structurally characterized. Complex 1 is a 2-fold interpenetrated three-dimensional framework, which to our knowledge represents the first interpenetration example of coordination framework with unique (3,6)-connected loh1 topology. Furthermore, the magnetic properties and photocatalytic activity have been investigated. As a result, complex 1 displays a weak antiferromagnetic interaction among the Mn(II) centers and good photocatalytic activity for the degradation of methyl orange solution under ultraviolet light irradiation.
TL;DR: In the past decade, various novel technologies have emerged with great potential to inactivate Salmonella and other foodborne pathogens, such as ozone, ultraviolet light, ultrasound, electrolyzed oxidized water, high pressure carbon dioxide, and bacteriophage as mentioned in this paper.
TL;DR: Clinical findings with pathogen‐reduced plasma have provided an impetus to the US Food and Drug Administration to promulgate specific requirements for approval of novel plasma products, some of which may be too burdensome for the industry to readily overcome.
TL;DR: Analysis of single-nucleotide polymorphisms in the LOX gene provided strong genetic evidence that LOX variants lead to increased susceptibility to developing of keratoconus.
Abstract: Purpose.
Keratoconus is a bilateral noninflammatory progressive corneal disorder with complex genetic inheritance and a common cause for cornea transplantation in young adults. A genomewide linkage scan in keratoconus families identified a locus at 5q23.2, overlapping the gene coding for the lysyl oxidase (LOX). LOX encodes an enzyme responsible for collagen cross-linking in a variety of tissues including the cornea. Corneal collagen cross-linking with long-wave ultraviolet light and riboflavin is a promising new treatment for keratoconus. To determine whether LOX is a genetic determinant of the pathogenesis of keratoconus, we analyzed association results of LOX polymorphisms in two independent case-control samples and in keratoconus families.
TL;DR: Copper porphyrin-sensitized TiO2 photocatalyst showed excellent activity for the photodegradation of MO whether under visible or ultraviolet light irradiation and Natural Bond Orbital charges analysis showed that methyl orange ion is adsorbed easier by CuP-TiO2 catalyst due to the increase of induced interactions.
Abstract: The photocatalytic activity of meso-tetraphenylporphyrins with different metal centers (Fe, Co, Mn and Cu) adsorbed on TiO2 (Degussa P25) surface has been investigated by carrying out the photodegradation of methyl orange (MO) under visible and ultraviolet light irradiation. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance UV (DRS-UV-vis) and infrared spectra. Copper porphyrin-sensitized TiO2 photocatalyst (CuP-TiO2) showed excellent activity for the photodegradation of MO whether under visible or ultraviolet light irradiation. Natural Bond Orbital (NBO) charges analysis showed that methyl orange ion is adsorbed easier by CuP-TiO2 catalyst due to the increase of induced interactions.
TL;DR: This review article describes the most important long-term treatment options for atopic dermatitis, which includes emollient therapy, the novel concept of proactive treatment, the different ultraviolet light modalities and a selection of systemic immunosuppressive drugs and biologics.
Abstract: Atopic eczema, also known as atopic dermatitis, is a frequent, highly pruritic, chronic skin disease, which is typically running in flares. The traditional treatment mainly consists of the reactive application of topical anti-inflammatory agents such as topical corticosteroids and topical calcineurin inhibitors. The short term benefit of this approach is well known, but long term remission between flares is difficult to achieve. Therefore, innovative long-term treatment strategies targeting flare prevention and skin barrier stabilization are needed. We and others have shown that normal looking, non-lesional skin of atopic dermatitis patients is immunobiologially not normal but characterized by an invisible inflammation and barrier defect. This has led to the novel concept of proactive therapy, which is defined as long-term, low-dose intermittent application of anti-inflammatory therapy to the previously affected skin, together with an ongoing emollient treatment of unaffected skin. This review article describes the most important long-term treatment options for atopic dermatitis, which includes emollient therapy, the novel concept of proactive treatment, the different ultraviolet light modalities and a selection of systemic immunosuppressive drugs and biologics. Current trial data, licensed indications, off-label use and relevant side effects of the different treatment modalities are summarized.
TL;DR: In this paper, a blend of orange and carrot juice was processed by three selected treatments combining pulsed electric fields (PEF), ultraviolet light (UV) and high intensity light pulses (HILP) with manothermosonication (MTS) technology.
TL;DR: A possibility that some characteristics of bacteria can retain or recover through photore activation, and a safety concern about pathogenicity revival might need to be considered with UV disinfection and photoreactivation is revealed.
TL;DR: In this article, the authors demonstrate that a low concentration of multi-walled CNTs does not affect the thermal response of the polymers but does significantly enhance their response to infra-red (IR) and visible light.
Abstract: Liquid crystal elastomers (LCEs) are of considerable interest for their potential as actuators, due to the ability of aligned monodomain LCEs to reversibly change their bulk dimensions in response to a phase change. Many LCEs reported in the literature will contract in one dimension in response to a temperature change or irradiation with ultraviolet light. For practical applications, photo-actuation is a more useful technology than thermal actuation due to the achievable speed and localization of the response. The use of UV light sources to ‘switch’ the materials is impractical, however, due to considerations of both safety and cost. Sensitization of LCEs to light of higher wavelengths may be achieved by mixing a small concentration of carbon nanotubes (CNTs) into the polymer matrix; CNTs will absorb light over a large range of wavelengths, and convert it into local heat, thus triggering the required phase changes in the LCE. In this article we demonstrate that a low concentration of multi-walled CNTs does not affect the thermal response of the polymers but does significantly enhance their response to infra-red (IR) and visible light.